Despite the discovery of over 1400 potential cancer biomarkers, translation of the discovery into clinical application has been very slow due to the lack of well-validated quantitative methods for assaying protein levels. Methods combining immune-enrichment of peptides derived from low abundance proteins and stable isotope dilution with mass spectrometry (MS), so-called SISCAPA-MS, are a promising approach for quantitative analysis of multiple peptide analytes in parallel. This method requires the availability of high affinity antibodies against large panels of proteotypic peptides for each of these potential biomarkers. To overcome the limitations of mouse hybridoma technology with peptide antigens, and the non-renewable nature of rabbit polyclonal antibodies, we propose to combine the robust immune response of rabbits to peptide antigens with AvantGen's proprietary yeast display system to isolate high affinity rabbit monoclonal antibodies against cancer-related peptides. During this Phase II study, antibodies against 100 peptides will isolated from yeast display antibody libraries constructed with antibody genes isolated from spleen or B cells from rabbits that have been immunized with peptide conjugates. The isolated antibodies will be of high affinity, renewable and can be produced in an economical manner.